Vulcanization of rubber



Patented Feb. 1, 1949 UNITED STATES PATENT oFFmE 2,46Q,393 VULCANIZATION F RUBBER Philip '1. Paul, Naugatuck, Conn., assignor to United States Rubber companypNew York, N. Y., a corporation of New Jersey No Drawing. Application June 23, 1945, Serial No. 601,313

14 Claims.

This invention relates to the vulcanization of rubber and similar suliur-vulcanizable rubber- I have found that primary amine derivatives of certain substituted-aryl sulfenamides which ordinarily alone have no substantial accelerating power, compared to the corresponding secondary amine derivatives, particularly in carbon black stocks, nevertheless act as delayed action activators with nitrogen-containing vulcanization ac celerators since they impart to a combination of them and a primary accelerator of vulcanization less activity at low temperatures than athigh temperatures.

These delayed action activators subscribe to the general formula ArylS-NHR where aryl is a carbocyclic ring of the benzene, naphthalene or biphenyl series having a nuclear-carbon directly attached to the sulfur, and which nucleus is further substituted by a group more electronegative than hydrogen (see Remick, Electronic Interpretations of Organic Chemistry, John Wiley & Sons, New York, pages 26, 30)

e. g., halogen, nitro, acyl (-COR), carboxyl,

(-COOH), carboxy ester (--COOR), sulfonamide (SO2NH2), acyl amide (-CONHz) and where R is an aliphatic or aromatic hydrocarbon group, Exemplary of the radicals falling in the scope of R are open-chain and closed-chain alkyl and cycloalkyl radicals, and aryl radicals, such 1 as methyl, ethyl, propyl, butyl, amyL cyclohexyl,

allyl, benzyl, bchloroethyl, b-methoxy ethyl, bamino ethyl, phenyl, tolyl, xenyl.

Exemplary of preferred sul'fenamides are:

N-methyl o-nitrophenyl sulfenamide N -ethyl o-nitrophenyl sulfenamide N-ethyl m-nltrophenyl sulfenamide N-ethyl p-nitrophenylsulfenamide N-ethyl 2,5-di-chlorophenyl sulienamide N-methallyl o-nitrophenyl sulfenamide N-phenyl o-nitrophenyl sulfenamide N-p-tolyl o-nitrophenyl sulfenamide.

Among the useful nitrogen-containing accelerators, employable with any of theabove sulfenamides,arethe followingz Acetaldehyde-aniline' condensation "productsj Acetaldehyde-butyraldehyde aniline--product v Acetaldehyde-formaldehyde-aniline product i Acetaldehyde-p-toluidine aniline product Alpha-ethyl beta-propyl acrolein-aniline product Irlhutylidene aniline Butyraldehyde-monobutylamine product Formaldehyde-aniline product Formaldehyde-monoethyl amine product Formaldehyde-para toluidine product Diphenylguanidine 5 Di ortho tolylguanidine Triphenylguanidine Z-mercapto' thiazole ib-dimethyl Z-mercapto thiazole 4-ethyl 2-mercapto thiazole Z-mercapto benzothiazole 2,2'-benzothiazole disulfide Zinc Z-benzothiazole sulfide Dinitrophenyl Z-benzothiazole sulfide Phenyl amino methyl 2-.benzothiazole sulfide Bis-N,N-(2-benzothiazyl thiomethyl) urea Benzoyl 2-benzothiazyl sulfide Benzothiazyl 2-monocyclohexyl sulfenamide Z-mercapto thiazoline Z-mercapto 4-methyl thiazoline Tetramethyl thiuram monosulfide Tetramethyl thiuram disulfide Zinc dimethyl thiocarbamate Tetra ethyl thiuram disulfide Lead dimethyl dithiocarbamate.

Thepreferred activators subscribe to the for-' where A is a saturated or unsaturated aliphatic ed or not. These chemicals are broadly primary amine derivatives of o-nitro thiophenol. The primary amine may be either a mono-amine or a diamine. V

' In the case of a primary diamine, either one or both of the amino (NHz) groups may be substitutedby the o-nitro phenyl sulfide radical. To illustrate, with ethylene diamine or polyethylene diamine H s-N-rom-oHm-NH,

where n is one or a multiple of one. The chemicals may also be described as o-nitro thiophenols in which the mercapto hydrogen atom is replaced by an amino radical in which the trivalentamino-nitrogen atom is linked to hydrogen and also to a hydrocarbon group.

The use of the materialsdenoted as delayed action activators ior the primary vulcanization [Scorch tests 75- minutes at 5 pounds per squareinch'stea-m pressure] accelerators, in addition to imparting a more A D favorable scorch factor, also allows greater free- Y dom of compounding variation. By va rying the T E T E T E T E ratios of accelerator and activator it is possible to obtain a. series Of combinations vary, 92 32 2 342 559 7 330 20 in scorch and curin properties. Indeed, in some I V V cases it may be founddesirable to use a Tmeans tensilestrengthin pounds per square inch. ponderance of the activator so as to have a rub- 10 E means p centelvngatwnber stock that is extremely safe and yet not too highly Cure Consequently, the ratio of' actl- Stocks A and B, and stocks C and D should vator to accelerator is to be chosen, dependent be compared. Stocks A and C, although apparon the type of rubber (natural or synthetic), type ently the same, Were compounded at diflferent of stock v(.vvhite stock, tread stock, etc.), temperatimes. The differencesin modulus and tensile e of ur time OfCIIrethe p r lar pr mary of stocks A and C are explained as due to the accelerator, for example, in the case of mercapto prolonged ageing of the broken down master benzothia'zole, the proportion of. activator gcnbatch of rubber and carbon black. erally ranges from to 200%, by weight, based 2 on the weight of the mercapto benzothia'zole and 0 g g lastly the obJectlves of the .compounder, 1. e., Whether he desires to provide a low or high modulus stock, to provide for a'short or a long Master batch B cure etc. s

r moked sheet 100 The preparation of these activators generally 5 Carbon black a, 45 involves the reaction or an aryl sulfunchloride Zinc p coconut Oil acids 35 and a primary aliphatic or aromatic amine, such Pine 35 as is described by Billman and OMahony, Journal Zinc g 50 of the American Chemical Society 61, 2340 (1939). sulfur 33 The following examples, in which the parts are by weight, are given'to illustrate the invention: 1600 EXAMPLE 1 Master batch A Smoked sheet 100 E F G l H I Carbon black -s r 45 35 M t B thB 160 100 100 160 160 i soap 0f coconut 011 ands Mzieg toignzuthiazoiah 1,0 0.5 0.5 z tar 3-5 N-lgl lfethyluo-nitrophenyl 0 35 inc oxide 5 0 S enaml r v 1-, ll flll 3.0 40 ifigtlitgfiiifgfl tgg 0.35 L: Jr n 2 Acetone diphenylamine condensate (anti E %?g oxidant) 1.0 sulfenamide, 0. 35

161.0 [Cured and minute's'at 30 poundsper square inch steam pressure] 7 M t r P 0 nt I as Esta, a G l H I 1,200 980 800 800. 800 2, s90 2,180 2,290 2,250 2,170 3,290-623" 3,100-030 3,09%13 2, 970-015 3,050-630 1 10 1,190 1,150,, 010 1,010 2, 840 2, 700 2, 410 2, 480 2, 500 3,200-51s 3,22e592, 3,220-033 2,990-553- a, 200-600 A B O 1) Master Batch A 161. 0 161.0 161. 0 161.0 Mercaptoben'zothiazole; e. 1. 0 0. 5 1.0 0. N-Gyclohexyl o-nitrophenyl sul- Ienamide 0. 35 N-Phenyl o-nitrophenyl sulfenamlde 0. 54

[Scorch tests 75 minutes at5 pounds per square inch steam pressure] E V V, .3 .7

T E T E. CI

Exam/n ne 3 Master been a u A GRr-S (butadiene-styrene emst mer) C'oaltar type softener 3.0 Sulfur 2.0 Carbon black 50.0 Zinc oxidefifinenn 1 5.0

[Cured 30 and 45 minutes at 30 pounds per square inch steam pressure] Minutes of Cure I Per Cent Elongation J i K [Scorch tests 75 minutes at pounds per square inch steam pressure] T E T I E 260 916 43 l 876 Tetramethyl thiursm monsulfide N-Oyclohexyl o-nitrophenyl sulienamide [Cure (145 and 60 minutes at 30 pounds per squareinch steam pressure] Minutes of Cure L Per Cent Elongation [Scorch tests 70 minutes at 10 pounds per square inch steam pressure] 'r E r E EXAMPLE 5 Master batch D [Cured 15 and30 minutes at 30 pounds per square inch steam pressure] Minutes of Cure 7 Per Cent Elongation N O Break 2, 590-620 Scorch tests 20 minutes at 5 pounds per square inch steam pressure] It is to be understood that the term a rubber is. employed in the claims in a generic sense to referto natural as well as synthetic rubbers which are capable of vulcanization when heated with sulfur, and includes caoutchouc, balata, gutta percha, polybutadienes, and modified polybutadienes, such as GRS and GRN (respectively, butadiene-styrene copolymer rubber, and butadiene-a-crylonitrile copolymer rubber), as well as latices and reclaims of such materials, whether or not admixed with pigments, fillers, softeners, antioxidants, etc.

Other ratios of the compounding ingredients than those mentioned in the examples given, as well as other Well-known fillers, pigments, etc., may be employed in the production of various types of rubber compounds, and are apparent to those skilled in the art to which the invention pertains.

Having thus described my invention, what I claim and desire to protect by Letters Patent is;

- 1-. A methodof vulcanizing a sulfur-vulcanizable rubber which comprises incorporating therein sulfur, a small amount of a primary organic rubbar-vulcanization accelerator, and an activator having the general formula Ary1--SNH,R where aryl represents a carbocyclic rin having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a group more electro-negative than hydrogen selected from the class Consisting of halogen, nitro, acyl, c'arboxyl, carboxy ester, sulfonamide, and acylamide, and R is a member selected from the group consisting of aliphatic and aromatic hydrocarbon groups.

2. A sulfur-vu1canizable rubber composition containing sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the general formula sulfur, a smallamount of a primary organic rubber-vulcanization accelerator, and an activator having, the general formula Aryl-SNHR where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S,

amazes and which nucleus is further substituted-by a. nitro group, and R is a member selected from the group consisting of aliphatic and aromatic hydrocarbon groups. 1

i. A sulfur-vulcanizable rubber composition containing sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the general formula where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further susbtituted by a nitro group, and R is a member selected from the group consisting of aliphatic and aromatic hydrocarbon groups. 7 A

5. A method of vulcanizing a sulfur-vulcanizable rubber which comprises incorporating therein sulfur, a small amount of a primary organicrubbear-vulcanization accelerator, andan activator having the general formula Aryl--SNH--R where aryl represents a benzene ring having a nuclear carbon atom directly bonded to the S, and which nucleus 'is further substituted by a group more electro-negative than hydrogen selected from the class consisting of halogen, nitro, acyl, carboxyl, carboxy ester, sulfonamide, and acylamide, and R is a member selected from the group consisting of aliphatic and aromatic hydrocarbon groups.

6. A sulfur-vulcanizable rubber composition containing sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the general formula where aryl represents a benzene ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a nitro group, and R is a member selected from the group consisting of aliphatic and; aromatic hydrocarbon groups.

-7. A sulfur-vulcanizable rubbery butadienestyrene copolymer composition containing sulfur, a small amount of a primary organic rubbervulcanization accelerator, and a compound having the general formula Aryl-S-NHR where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a group more electro-negative than hydrogen selected from the class consisting of halogen, nitro, acyl, carboxyl, carboxy ester, sulfonamide, and acylamide, and R is a member selected from the group consisting of aliphatic and aromatic hydrocarbon groups.

8. A sulfur vulcanizable rubbery butadienestyrene copolymer composition containing sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the general formula Aryl--S--NI-IR where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a nitro' group, and R is a member selected from the group consisting of aliphatic and aromatic hydrocarbon up's.

9. A method of vulcanizing a sulfur-vulcanizable rubber which comprises incorporating therein sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the general formula ArylS-NH'R where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S,

and which nucleus is further substituted by a group more electro-negative than hydrogen selected from the class consisting of halogen, nitro, acyl, carboxyl, earboxy ester, sulfonamide, and acylamide, and R is an iso-propyl radical.

10. A method of vulcanizing a sulfur-vulcanizable rubberwhich comprises incorporating therein sulfur, a' small amount of a primary organic rubher-vulcanization accelerator, and a compound having the general formula Aryl--SNH--R where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a group more electro-negative than hydrogen selected.

from the class consistingv of. halogen, nitro, acyl, carboxyl, carboxyester, sulfonamide, and acylamide, and R is a cyclohexyl radical.

11. A sulfur vulcanizable rubber composition containing sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the general formula where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a group more electro-negative than hydrogen selected from the class consisting of halogen, nitro, acyl, carboxyl, carboxy ester, sulfon-amide, and acylamide, and R is'an isopropyl radical.

12. A sulfur-vulcanizable rubber composition containing sulfur, a small amount of a primary organic. rubber-vulcanization accelerator, and a compound having the general formula where aryl represents a carbocyclic ring having a nuclear carbon atom directly bonded to the S, and which nucleus is further substituted by a group more electro-negative than hydrogen selected from the class consisting of halogen, nitro, acyl, carboxyl, carboxy ester, sulfonamid'e, and acylamide, and R is a cyclohexyl radical,

13. A method of vulcanizing a sulfur-vulcanizable rubber which comprises incorporating therein sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the formula where R is an isopropyl radical.

14. A method of vulcanizing a sulfur-vulcanizable rubber which comprises incorporating therein sulfur, a small amount of a primary organic rubber-vulcanization accelerator, and a compound having the formula .SNR

where Risa cyclohexyl radica1.

PHILIP T. PAUL.

REFERENCESCITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name; Date 2,333,468 Cooper Nov. 2, 1943 2,382,813 Paul Aug; 14, 1945 

